I'm using an earlier 4L80E and the trans only has one 2 pin connector and the round 20 pin.

I'm confused between ISS(Input Speed Sensor) and VSS(Vehicle Speed Sensor) I'm assuming I plug the ISS into my harness but what about VSS?

The harness I'm using is from a 2000 Silverado originally equipped with a 4L60E.

 

ISS and VSS are the same type physical sensor. I think the terminology comes from where they are at in the transmission. One up front is called an ISS since it's looking at the input revolutions to the transmission. VSS for the rear reading the output of the transmission and hence the actual speed after gear multiplications.

I'm not really an expert on all the transmissions. Didn't know that early 80e's only had 1 speed sensor? Regardless you will have to have 2 sensor inputs to a 2000 model year PCM or the transmission will not function properly.

 

4WD? If so, the VSS will be the rear sensor on the T-case and the existing harness will connect there. The ISS will be connected to new wiring you have to add to the pcm connector. https://www.performancetrucks.net/fo...d.php?t=413157

 

Nope, the tranny is not a 4wd. The 2000 silverado harness was likely a 4wd.

 

Is there a spot to install the second sensor as in these pics?

 

My bad, there are two connectors one was painted over. So the one towards the front is ISS and the rear is VSS. Since I have both of these then I shouldn't need to wire anything to the pcm, since my harness appears to have both...

 

If it is a 60E harness you will have to correct the wiring as described in the link above so that the ISS connector is wired to the proper pins at the PCM. The wiring for the main connector must also be re-arranged.

Your second connector is actually wired for the front drive output speed sensor on the t-case if it is a 60E 4WD harness.

 

Greetings, im still trying --and have never had such trouble trying to get the answer on any internet forum,
my 2000 still has the old 4 plug blach box computer, the round plug rewire, routine, when you got the two left over wires,, what location do they go to on the old 4 plug black box connectors?????????


no one has posted the info, its crystal clear if you got the newer red blue 411 type pcm, but for those of us swapping a 4l80e in a 4.3 v6 truck,,,,
we cannot get that last detail of where the last two wires are plugged --or replugged into on the 4 plug connector.

 

this is the closest I have come to getting any info.


ecu pinout diagram - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat
the black connector #3 and #4 are vss locations and
the blue connector #29 is vss low
#30 is Vss high.


but I still don't know what two to change at the connector after rewiring the round plug-- when I add a pigtail to plug into the front sensor, two of these 4 plugs are the location.......................

 

See here: https://www.performancetrucks.net/fo...413157/page16/